Easy,Green and Safe Carbonylation Reactions through Zeolite‐Catalyzed Carbon Monoxide Production from Formic Acid

Zeolites with the right shape and acid site density and strength, such as certain ZSM‐5 forms, were able to cleanly decompose formic acid to carbon monoxide (CO), and the latter could be directly used in palladium‐catalyzed carbonylation reactions. A simple two‐reactor system was designed to produce CO conveniently and then further react this gas in a safe way. The two‐reactor system is particularly cheap, easy to set up and use. In addition, the carbonylation conditions without pressure allowed for very efficient CO incorporation, with only 1% of palladium(II) chloride (PdCl₂) and Xantphos.

     

硅烷自组装膜对制备于多孔性基底上导电聚吡咯薄膜性能的影响

采用硅烷偶联剂对在多孔性绝缘Al2O3膜基底上形成的导电聚吡咯(polypyrrole, PPy)薄膜的形貌及导电性能进行了改善,并探讨了硅烷自组装膜与导电PPy薄膜的形成机理.用硅烷偶联剂对Al2O3膜表面进行改性后,形成了与基底牢固结合的硅烷自组装膜,然后通过化学聚合法在自组装膜上制备得到了均匀致密的PPy薄膜.结果表明:硅烷偶联剂有效地改善了PPy薄膜的均匀性及其与基底的附着性,电导率从5.4S/cm提高到了16.6S/cm.     

Catalytic contribution of reactor wall materials on oxidative coupling of methane

Gas-phase oxidative coupling of methane (OCM) was investigated with empty tubular-flow reactors made of various materials (quartz, ceramic and stainless steel tubes). When the temperature is higher than 680°C, the CH₄ conversions in three kinds of empty reactors are measurable, and the gas-phase OCM becomes noticeable at 750°C or higher. High temperature is beneficial to the activation of CH₄ and the dehydrogenation of C₂H₆ to C₂H₄. Residence time of reactants in the heated volume plays an important role in the gas-phase OCM. Experiments indicated that the gas-phase OCM can be minimized by increasing reactant gas velocity or filling the free volume of the reactor with inert materials. Reactor surface also has an effect on the reaction and may participate in some surface reactions. Based on the kinetic results and the SEM investigation on the surfaces of reactors, a gas-phase reaction mechanism of OCM is proposed.     

地闪电磁脉冲对近地电缆外导体的耦合研究

采用时域有限差分法计算得出地闪回击电流近场在地面附近的分布,将场值代入离散化后的传输线方程后,计算了近地电缆外导体上的感应电流,分析了大地电参数、导线架高、长度以及与雷击通道距离等因素对感应电流的影响.计算结果显示,距雷击通道200m以内的近场对敏感设备及系统构成的威胁最为严重,应作为地闪电磁脉冲环境预测研究的重点.     

The oxidative coupling of methane by sodium promoted lanthanide catalysts

The characteristics of La₂O₃ catalysts with three different supports (BaCO₃, MgO, and ZnO), two different alkaline metal promoters (Na₂O and Na₂CO₃), and a china clay have been investigated. The relationship of the surface basicity of the support to the activity and selectivity of the catalyst were studied by TPD. The results showed that the surface basicity of these three supports decreased in the following order: BaCO₃ > MgO > ZnO. The choice of Na₂O as a promoter in La₂O₃/(BaCO₃ or MgO) had a better effect than the choice of Na₂CO₃. The Na₂O promoter could increase not only the catalytic activity and the C₂ selectivity, but also lower the optimal reaction temperature. Addition of 15% clay into the La₂O₃–alkaline metal catalysts could increase the strength of the catalyst and lower the optimum reaction temperature.     

Causal Effects of Aroma Compounds on Royal Gala Apple Flavours

Volatile flavour compounds produced by Royal Gala apple have been identified by GC-MS. Major components were 2-methylbutyl acetate, butyl acetate, hexyl acetate, butanol, 2-methylbutanol and hexanol. Odour-port evaluation of the components separated by GC indicated that the first four compounds were important contributors to the aroma and flavour. Use of analytical sensory panels revealed that 2-methylbutyl acetate, butanol and hexyl acetate had the greatest causal effect on those aroma and flavour attributes considered important for Royal Gala apples.     

Total integrated reflection loss in a laser diode to single-mode fibre coupling system

A geometrical optics approach is used to analyse the reflection of a divergent beam falling onto a concave or convex surface. The polarisation state of a ray in the incident beam depends on the position where the ray impinges upon the surface. The distribution of transmittance over the surface for different polarisation states is determined. An integration of the transmittance distribution determines the total reflection loss of a coupling lens used in a laser diode to single-mode fibre coupling system.     

一种高性能的谐波检测数字低通滤波器

谐波检测的准确性和实时性是影响有源电力滤波器的重要因素.文中采用指数平均低通滤波器,并利用级联技术,解决了数字信号处理器有限字长与谐波提取的准确性和实时性之间的矛盾.将其用于串联混合型有源电力滤波器中,实现了高性能的谐波检测.实验结果证明了所提出的理论的正确性.     

空间磁化等离子体非线性受激电磁辐射进展

电磁波和磁化等离子体的非线性相互作用复杂,高功率电磁波调控电离层实验提供了研究非线性基本问题的主动方式.为构建空间磁化等离子体受激电磁辐射(stimulated electromagnetic emissions,SEEs)体系,本文首先总结了磁化等离子体中可能发生的参量不稳定性;其次,回顾了近十年国际电离层加热激发S...     

稀土萃取过程的广义预测解耦控制

考虑稀土萃取过程具有多变量、强耦合特性,提出一种基于广义预测解耦控制(GPDC)的稀土萃取过程控制方法.首先针对模型未知的强非线性稀土萃取过程,构建基于极限学习机的组分含量系统模型,并依据模型特点设计多个稀土萃取过程GPDC控制器;然后为降低各控制回路间的耦合性,在控制器的性能指标中引入校正策略,通过回路中模型预测值与...